


Catalyst

by thinkpink20



Category: Sherlock (TV)
Genre: M/M, Multi, Sibling Incest, Threesome - M/M/M
Language: English
Status: Completed
Published: 2012-02-24
Updated: 2012-02-24
Packaged: 2017-10-31 16:24:03
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,563
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/346110
Author URL: https://archiveofourown.org/users/thinkpink20/pseuds/thinkpink20
Summary: <blockquote class="userstuff">
              <p>John realises he's simply a catalyst</p>
            </blockquote>





	Catalyst

**Author's Note:**

> From [a prompt](http://sherlockbbc-fic.livejournal.com/2727.html?thread=6514599#t6514599) on the Sherlock kinkmeme, sort of continuation of 'French', though you don't have to have read that to understand this. (Also personally I blame [this clip,](http://www.youtube.com/watch?v=Ib_4xREEh8g&feature=related) specifically the way he looks at her at 0:30s. So technically this is Benedict's fault.)

Sherlock has never joined in. He watches - sometimes more intently than others - but he has never actually touched, not even so much as a whisper of breath.

Until tonight.

Maybe it's the tight, elastic high of having just solved a case (a high profile one too, Lestrade's team mentioned specifically in the paper, splashed in blue-black print), but tonight is going to be different. John can feel it before it even begins.

Sherlock has barely finished throwing off his scruffy blue scarf before he is reaching for his mobile, tapping in numbers. "Time to call Mycroft, I think!" Is all he says, still all rapid movement and sharp pleasure from the triumph of bagging not one but two murderers. His eyes still look dangerously pleased. John wouldn't stop him for the world.

Mycroft arrives promptly two minutes after they've finished eating, as though he knew this all along. Maybe he did. He comes carefully into the room, twirling the umbrella in a lazy sort of way.

"Congratulations on the case," he says, smiling easily at John. It's a smile John has become quite used to.

"Thank you."

"Are we on the front page of the evening edition?" Sherlock asks, pouring out a fresh glass of wine. This is the first sign that something is different - John notes it with the air of a man who has been living between the Holmes brothers long enough.

Mycroft senses it too, because his body language stalls for a moment. It's almost imperceptible, but John notices it because there are some things you come to learn when you've had someone inside you, the precise tick of their body.

"Indeed," Mycroft nods once, taking the glass. "Street vendors everywhere are hallowing your name."

Sherlock smirks at this, just one side of his mouth arching up, smug and clever. That's the second sign.

John looks to Mycroft to share it, this new turn, but Mycroft is already looking away. 

For a little while things fall into their usual routine - if this can ever be called anything like 'usual'. John and Mycroft settle on the sofa, John explains the case in that simple, matter-of-fact way he has perfected from the blog and Mycroft listens like it's the first time he has ever heard one of Sherlock's stories. He burrows a necessary frown when the murderer is mentioned, smiles politely when a deduction is revealed. He's like a grateful member of the audience at a pantomime, attention never wavering despite already knowing the outcome of the farce. And all the while Sherlock sits in his usual seat in the corner, silent like a ghost but still very, very present. John finds he's not surprised when he doesn't feel the usual level of urgency radiating from him like a pin-pulled grenade, somehow already knowing that this is the third sign.

Though the sign for what, of course, he still doesn't know. 

When the story is over Mycroft politely takes John's glass from his hand and places it down on the table. He takes his time draining his own dregs, letting John watch his throat working carefully, head tilted at the precise angle so that Sherlock can also see, also admire. Mycroft - more than anyone else John has ever met - is acutely aware of his own sensuality. He knows the delicious bow his lips make when he raises a glass to them, uses it wisely.

And then in that careful, methodic way he is kissing John's mouth, moving away just far enough to make John follow for more, meet him in the middle. It's far more intoxicating than the wine. And though John still knows there have been Signs from Sherlock, he forgets them briefly as Mycroft works his knee insistently, always starting in the same place. 

John feels a thrill of expectation dance up his spine, parts his legs easily for Mycroft's hand but also for Sherlock's eyes. He likes very obvious displays, John has found, and he shows no point in disguising the fact he is already hard, worked into such a state by Mycroft's fingers kneading his thigh and his tongue, slip-sliding like a promise.

It's only when John gasps himself, loud and instinctive at the feeling of Mycroft palming him obviously through his jeans, that he realises Sherlock hasn't yet made a sound. Not even the slow, warm curling noise of appreciation that he usually gives when Mycroft's fingers finally reach the top of his in-seam.

This is sign number four.

Still locked into an increasingly wet, distracting kiss, John briefly worries his silence means Sherlock has gone, deserted them and disappeared. He turns his head carefully, offering Mycroft the clear, pale skin of his neck whilst he drags his eyes open and focuses them on the seat in the corner of the room, Sherlock's usual watching place.

He's still there, but what John sees causes an instant, bitten off groan to form in the base of his throat. He manages to stifle it quickly so that he doesn't draw attention to himself because John wouldn't dare to disturb the look Sherlock is giving Mycroft at that very moment. It's almost indecent ( _is_ indecent, John reminds himself - he's his brother) and it's so intimate that John almost looks away, like it's something far too private for his eyes. But the heat buried between his thighs won't actually _let_ him look away, and so he watches as Sherlock sub-consciously licks his lips, presses two teeth into the plump, bottom one and watches the movement of Mycroft's mouth on John's neck. He looks - John realises - not all that especially unlike himself. He looks hungry.

Deliberate, attentive fingers squeeze John through the practical denim of his jeans and he refocuses on Mycroft, feels his own eyes flutter shut as a tongue brushes his lips again, licking at his mouth.

"Bedtime, John?"

He can barely think straight to answer.

Their usual set pattern is simply not to close the door; Sherlock follows an undetermined number of moments later, almost as though he was casually wandering the house and stumbled upon them rather than following them pointedly from the living room. But tonight that's different too; John feels him rise from the chair at the same moment they do.

Which obviously, then, would be sign number five.

The telling thing is that John now wants to touch him, as though his disobedient, stupid body takes this minute deviation in the plan as permission to go for what he originally wanted, back before all this started. His fingers almost reach out to tug at Sherlock's buttons rather than Mycroft's, though he manages to corral them in time. The noise of three sets of footsteps crossing the landing, going into Sherlock's room, sounds unusual to his ears. He feels hyper-aware of everything, almost stumbling on the threshold and grateful of Mycroft's silent, steady hand in the small of his back to guide him to the bed.

When they get in there, onto the cool sheets amongst Sherlock's disordered mess, John briefly forgets. Mycroft is undressing him, which frankly is an action distracting enough for any sane human being, and the increased air of tension seems to have gone directly to his blood stream, making John reach and grasp for Mycroft's mouth, lips, tongue. He wants him everywhere, and polite as ever, Mycroft obliges. John surrenders himself easily to the desire to rub against the familiar, warm body pressed to him like a lazy cat and approvingly Mycroft's fingers stroke at him, pulling him closer, aligning their hips until he finds an angle John didn't even know he wanted.

He hears the noise of Sherlock's chair creaking in the corner he's sure, but somehow it doesn't register what that means. Thus John is surprised when he feels the smooth, clear line of a body press up against his back seconds after the bed dips. He gasps, startled into Mycroft's mouth and turns his head to catch Sherlock's eye but he's already busy, planting cool, open mouthed kisses along the exposed line of John's shoulder. The sight - mixed with the feel of it - causes a spiral to start in John's self control. He can't take the two of them, he thinks. He can't, it's too much. Too good, too warm, too nice.

The subtle, lazy drag of Sherlock's fingertips up his spine causes John to moan, unguarded. He can't be expected to restrain his voice in such a situation, that's more than he can manage.

"John," Mycroft says, apparently unfazed by this new addition to their evening, and John lets his face be turned back, lets his mouth be kissed again. Have they done this before? With one of the others? Is Mycroft unfazed because this was simply what they were building up to all along, easing him in?

Something tells him no. That look, the one John can recall so vividly from the living room mere moments before - that's not the look you give to someone you've had before, however briefly. Plus John can tell from the taut, almost restrained lines of Sherlock's body against his back that this is new. For all of them. 

God knows how long Sherlock has been wanting this, but he's certainly never had it.

And then a strong, purposeful hand on John's hip distracts him, pulling him back. He presses firmly into Sherlock's body (he's hard, and oh - that causes John to swallow against Mycroft's mouth, body desperate at the thought) and feels the answering shift of Mycroft moving with him, closing the resulting gap. He's held tight, firmly between them now and John's mind spins with it, lost in the eager slide of bodies, maddening layers of cotton and denim lying frustratingly between them.

He's so lost in the sensations that John barely realises at first when Mycroft leaves his mouth for his neck, lips sliding down over sensitive flesh. He shudders at the cool air blown freshly onto his collarbone, then as though through a sleep he comes to realise where Mycroft is heading, up over the bare top of his arm and onto the warm skin of his shoulder. The shoulder Sherlock is still kissing slowly.

John manages to turn his head in time to watch the mouths that were once on him finally meet. It's seamless and he's reminded of watching heat-seeking missiles in the cloying heat of the dessert; they find their target perfectly, as though that was what was meant to happen all along, like nature. 

And the noise that Sherlock makes, like desperate, hard relief when Mycroft's lips brush his own convinces John all the more of it - it was each other they wanted, not him.

It should make him feel worse than it does, but for the moment John can't think as he watches Mycroft push his fingers into Sherlock's curls, mouth finding him over and over again until John can physically _feel_ the heat rolling off Sherlock's body. He shifts a little bit, onto his back so that Sherlock is half on top of him, reaching over John's body to pull at his brother. It gives a better view of them, obviously lost completely in each other now so that he's just a platform, just a flower sitting idly by for the bee and the pollen. 

And the sight of them - of course - is rather stunning. John watches as Sherlock's eyelids, half-mast, watch his brother between kisses. He looks drunk. If he was any more of a man he'd feel guilty for it, John thinks, getting this flush of heat all over his skin at watching this particular, indecent spectacle. But he doesn't, certainly not when he catches a glimpse of two tongues sliding against each other, feels the resulting shudder run through Sherlock's body where it's pressed so closely against his. The noise they're making too, affects John far more acutely than it should, the near obscene sound of wet lips moving against one another. He feels suddenly like a teenager again, watching something on the television that he shouldn't, way past his bedtime. But he's fascinated, can't look away.

Mycroft arches away from the kiss, forehead still grazing his brother's and strong fingers clearly still resting on his neck but his mouth teasing. John knows that feeling, empathises as he watches Sherlock tilt his chin, trying to get that sensation back, turning this way and that to catch Mycroft's mouth until he suddenly gives in, lets himself be caught. Sherlock groans in satisfaction as Mycroft rewards his efforts by licking at his swollen, bruised bottom lip that looks stained and red from their kissing. And John can _hear_ how lost Sherlock is, because he knows him, knows he would never make such an obvious display of his relief in everyday life.

Somehow - possibly because John himself was nowhere near coordinated enough earlier - Mycroft still has his shirt on, and John watches as usually-rational, clever fingers bunch up fistfuls of the expensive cotton in a fit of desperation. Sherlock's breathing is hard and erratic and uneven, but John didn't realise quite how _much_ until he hears him speak.

"Mycroft."

Sherlock's voice cracks and it's the sudden, startling sound of him saying his brother's name so unlike any way he's ever said it before that makes John realise - he shouldn't watch this. He shouldn't be here for this. 

Not because it's wrong (though of course it is wrong, his brain reminds him, which is something he suspects he could be talked out of if he lies here long enough looking at them) but because this actually has nothing to do with him. Maybe it never has. The only reason people ever get hit by lightening is because they're standing in the way of the lightening and the ground at the wrong time; it's not trying to hit _them,_ it's trying to hit the earth, where it was headed all along.

John is snapped out of his thoughts by the sound of Mycroft's familiar, clear, steady voice. "Here, Sherlock, here." He's trying to guide Sherlock's hand down to his shirt buttons, helping him work to get them open. He sounds just as patient as he ever does, but there is a reed in his voice that John realises he never quite managed to elicit himself - discomposure. Desire, yes. Want? No.

And that's what makes him go. 

John carefully edges sideways, lets Sherlock climb over him until there are two bodies pressed against each other instead of three. He grabs his shirt from where it has fallen on the floor and when he straightens up he can't help but steal one last look.

Mycroft's thigh is wedged firmly between Sherlock's legs, giving him something to rock against and John feels himself swallow hard as he watches Sherlock's closed eyes twitching further shut with pleasure each time Mycroft shifts against him. It causes John's skin to rush hot, the sight of their foreheads pressed, noses brushing as their kisses become more a brush of mouths, lost in the sensations. 

He realises there's absolutely no reason for him to still be here, so tearing his eyes away John turns and slips from the room. 

He goes out, walking - here, there and everywhere; anything to not be in Baker Street. But when he shuts his eyes against the glare of a tourist's camera flash as he crosses the road, he still sees them there behind his eyelids.


End file.
